Shares in the world's oldest running bank tumbled another 7 percent, to (EURO)0.23, on Thursday as the scandal at the bank got caught up in the campaigns for February's elections.

The Bank of Italy said in a statement that derivative purchases reported by the media were disclosed to it `'only recently after hidden documents were found" by the bank's new management. The central bank said both its oversight division and judicial authorities were reviewing the transactions.

Italian Economic Minister Vittorio Grilli said, meanwhile, that the government had been aware of problems at the bank for at least a year.